There are underbody convective blankets in the market. One of those blankets is described in U.S. Pat. No. 6,511,501. However, the '501 blanket is not meant to provide warmth to the head of the patient via convection. There are moreover a number of other blankets represented for example by U.S. Pat. Nos. 5,360,439, 5,384,924, 5,514,169, 5,632,769 and 5,839,133 that specifically have a recess at the head end of the blanket whereby the head of the patient lies.
There are some convective blankets that could warm the head of the patient. However, most of those blankets are for covering the body of the patient. An example of such blankets is disclosed in U.S. Pat. No. 5,928,274 in which the head portion of the blanket has a recess so that only the head of the patient is not covered by the blanket.
Also with respect to the prior art convective blankets, the apertures or holes whereby the warm air is output from the blanket usually are pre-punched before the two layers of the blanket are bonded so that the apertures are substantially evenly distributed across the sheet of the blanket that outputs the warm air. That being the case, the heated air output from the blanket is directed to the patient without much focus. Furthermore, for the prior art underbody blankets, at least with respect to those that are full body convective blankets, the channels that extend longitudinally along the blanket usually would extend all the way to the foot end of the blanket, so that the air input to the blanket flows substantially in only one direction. This means that by the time that the heated air gets to the foot end of the blanket, the warmth of the air has substantially diminished. Accordingly, there is a temperature gradient difference between the heated air output proximally to the air inlet port and the heated air output distally from the air inlet port.
A need therefore exists for a new type of underbody blanket that warms the head, as well as the body of the patient, with the warm air circulating about the blanket to maintain an even temperature throughout, and when output from the blanket, is focused to the patient.